Middle ear prosthesis having discrete projections for purposes of ossicular attachment

ABSTRACT

A middle ear ossicle prosthesis in which the component for ossicular attachment comprises a surface bearing a plurality of discrete projections facing the ossicle to which it is attached which minimize total contact between the prosthesis and the ossicle. The prosthesis may comprise a loop forming a partial circle for encircling an ossicle, a piston for transmitting vibrations from the loop to the inner ear, and a rod solidly connecting the loop to the piston. The loop may have an upwardly turned end to facilitate placement of the loop over the ossicle. The projections may be provided in one row, two rows, or may be otherwise arrayed, and may be dissimilar from one another in configuration and dimensions.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority benefit of U.S. Provisional PatentApplication No. 61/529,590, filed Aug. 31, 2011. This application is aContinuation of U.S. patent application Ser. No. 13/524,515, filed Jun.15, 2012, and published issued as U.S. Pat. No. 8,834,567 B2 to Scheureron Sep. 16, 2014.

BACKGROUND OF INVENTION

Numerous prior designs of ossicular prostheses have sought to establishfunctional continuity of the ossicular chain after damage to some or allof the ossicles secondary to disease or congenital anomaly. Frequently,when the stapes is damaged or diseased, re-establishment of a connectionto the inner ear via stapedectomy or stapedotomy is also required.Prostheses most often are designed to attach to remaining healthyossicles and replace the function of the ossicle(s) which are missing ordiseased.

In the case of the stapes, dysfunction often occurs as a result of adisease process called otosclerosis in which the footplate of the stapesbecomes fused to the surrounding bone and no longer effectivelytransmits ossicular motion to the fluids of the inner ear. Most stapesprostheses over the last several decades have been constructed of eithera circumferential, or nearly circumferential, wire loop or a broaderribbon-type (flat wire) loop, which directly attaches to the longprocess of the incus. More recently, clip-type prostheses have beendeveloped that are comprised of a complex-shape broad ribbon in which amore limited surface area of the incus is placed in contact with theflattened clip. In either case, the component for incus attachment isjoined to a piston that fits into a hole (fenestra) in the stapesfootplate created by the surgeon so that the piston can translateossicular movement to the fluids of the inner ear.

Ossicular prostheses, which have been designed to replace the functionof the stapes and attach to the incus, have frequently causednecrosis/erosion (loss of bone tissue) in the area of the incus to whichthey are attached, as well as the bone more distal to the prosthesisattachment. This bone loss in the area of the prosthesis attachment cancause loosening of the prosthesis and resultant hearing loss because ofpiston migration out of the hole in the stapes footplate and/orde-coupling of the motion from the incus to the prosthesis. Ideally, theossicular prosthesis, which is designed to replace the function of thestapes, will attach firmly and permanently to the long process of theincus without ever loosening or migrating away from its position ofplacement at the time of surgery. This is also true of prostheses thatattach to the malleus and replace the function of the other ossicles.

Bone/tissue loss in the area of the attachment of the stapes prosthesisto the incus is thought to be due to impaired blood supply to the longprocess of the incus after surgery. Prior to surgery, blood is suppliedto the area of the long process from both the body of the incus distallyto the long process, as well as from the opposite direction across thejoint where the incus is joined to the stapes. Since the attachmentbetween the stapes and incus is cut during surgery, the only bloodsupply to the long process of the incus after surgery flows distally tothe long process from the body of the incus. Accordingly, blood flow tosupply the area of the incus both at and distal to the prosthesisattachment ideally should not be restricted by the prosthesis itself. Itis widely believed that a prosthesis, which exerts sufficient mechanicalpressure on blood vessels/mucosa near the surface of the incus, cancause a restriction of blood flow sufficient to cause incus necrosis andsubsequent failure of the prosthesis.

Since the blood supply in the area of the prosthesis attachment istenuous after surgery and most prostheses have areas of very broad orcircumferential contact points with the long process, relatively largeareas where blood vessels or delicate mucosa are located can becompressed by the prosthesis and cause death of the underlying or distaltissues. Efforts to reduce both the amount and the surface area ofmechanical pressure exerted on the incus have resulted in new prostheseswith broader and/or softer ribbons to contact the incus; new methods ofcrimping to achieve optimal pressure on the incus (tight enough toensure good coupling of incus translation to that of the piston in theinner ear, but loose enough to reduce the chance of pressure necrosis);or a change in the shape of the ribbon or wire so that only opposingsides of the incus are grasped firmly. Nevertheless, all efforts to dateshare the common characteristic that at least some of the wire or ribbonis broadly in contact with the incus and consequently have the potentialto cause pressure necrosis to the underlying mucosa and loss of bone inthese areas of broad contact.

In the case of prostheses that attach to the first and most lateralmiddle ear bone (the malleus) to replace the function of the incus, thestapes, or both, the prosthesis is placed in contact with the medialportion of the malleus and the surrounding ear drum. The prosthesiscomponent which contacts the medial malleus typically comprises ashallow groove within a larger flat surface that contacts the inner eardrum surface surrounding the malleus. The medial malleus lies withinthis shallow groove. However, when patients stand up and walk aftersurgery, shearing gravitational forces commonly result in the prosthesisslipping out of position and “falling over” inside the middle ear space.This loss of prosthesis contact with the malleus and ear drum results inhearing loss. Continuing prosthesis contact with the malleus and drumafter surgery is initially dependent solely on the medial pressure themalleus exerts on the prosthesis. Accordingly, any design factor whichcould increase the resistance of the prosthesis-malleus interface to thegravitational shearing forces potentially displacing the prosthesis awayfrom the malleus would improve hearing outcomes.

SUMMARY

The present invention relates to the concept that if a relatively largepatch or area of contact between an ossicular prosthesis and an ossiclecan be avoided, then disturbance to the underlying mucosa and bloodvessels can be minimized with a reduction in the chance for necrosis.More particularly, broad contact may be minimized by a design in whichdiscrete projections from the prosthesis' ossicle interface surfacespace that surface away from the bone. Moreover, a very secureattachment between the ossicle and the prosthesis could be anticipated,due to the resistance to motion engendered by partial embedment of theseprojections in the ossicle. A more secure attachment would beanticipated to reduce the chance of prosthesis translocation followingsurgery, which can cause surgical failure even in the absence ofossicular necrosis.

It is an object of the invention to provide novel means of attachmentfor an ossicular prosthesis to an ossicle using a plurality ofprojections extending from a wire, loop, ribbon, clip, disc, or otherprosthesis surface form or configuration which would serve as contactpoints between the ossicle to which they are attached and the prosthesisfrom which they arise.

The projections can be of variable number, shape, length and arrangementaccording to the intended use in a particular patient's anatomy anddisease process.

The projections are designed to minimize the surface area of prosthesisto ossicle contact, thereby minimizing the potentially damaging effectthat broader contact may have, as described in “Background of theInvention.” They also may have the advantage of attaching to the ossiclevia embedment of said projections which is anticipated to reduce therisk of surgical failure further by reducing the risk the prosthesiswill move away from its position at the time of surgical implantation.

In one embodiment, the projections are envisioned as having sharp endswhich could enhance firm embedment in the ossicular mucosa and/or bonewith which they are in contact, creating a secure attachment with areduced amount of total contact between the prosthesis and the ossicle.

In embodiments, the prosthesis could be comprised of metal such astitanium with projections as described consisting of a differentsubstance, such as hydroxyapatite which could fully integrate withunderlying bone.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings, when considered in connection with the followingdescription, are presented for the purpose of facilitating anunderstanding of the subject matter sought to be protected.

FIG. 1 is a side view, not drawn to scale, of a prosthesis according toat least one aspect of the invention.

FIG. 2 is a perspective view of a prosthesis according to at least oneother aspect of the invention.

FIG. 3 is a cross sectional detail side view of a prosthesis accordingto a further aspect of the invention, and is drawn to enlarged scale.

FIG. 4 is a cross sectional side view of a detail of a prosthesisaccording to still another aspect of the invention, and is drawn toenlarged scale.

FIG. 5 is a side view, not drawn to scale, of a second embodiment of aprosthesis according to the present disclosure.

FIG. 6 is a side view, not drawn to scale, of a third embodiment of aprosthesis according to the present disclosure.

FIG. 7 is a side view, not drawn to scale, of a fourth embodiment of aprosthesis according to the present disclosure.

DETAILED DESCRIPTION

FIG. 1 shows a middle ear prosthesis such as a stapes prosthesis 5comprising a loop 3 which is formed as a partial circle of at least onehundred eighty degrees, or as shown, three hundred to three hundredthirty degrees, for encircling an ossicle such as an incus 1 (seen incross section in FIG. 1). It would of course be possible to arrange theloop 3 as a full circle, by adding an element which closes the gap whichexists when the loop 3 forms a partial circle as depicted and a suitablefastener for retaining the added element to the loop 3 (this option isnot shown). The loop 3 bears a linear array of projections or spikes 2,which may for example be arrayed as a row of spikes 2, which projectinwardly from the inner surface 6 of the loop 3, and which make contactwith the underlying incus 1. The terms projection and spike, both in thesingular and in the plural, will be used interchangeably herein.Inwardly signifies towards the center of the circle which would exist ifthe loop described a full circle. The surface 6 may be flat, curved, orcomplex. The loop 3 is attached by a rod 8 to a piston 4 which sits in afenestra (not shown) and communicates with the inner ear so as to passvibrations in a manner approximating that which would occur should allof the ossicles be functioning normally. It will be seen that only thepoints 7 of the spikes 2 make contact with the incus 1. This limits thepatch of contact between the prosthesis 5 and the incus 1 which wouldotherwise broadly occur with the inner surface 6. The piston 4 iscoupled to and terminates the rod 8.

The loop 3 may take various forms, such as a wire, ribbon, loop, orclip, disc, or other configurations.

The loop 3 may comprise an upturned end 9 located at that end of theloop 3 which is opposite the rod 8. The upturned end 9 may form an angleof greater than 90 degrees (not shown), which would enable the jaws of aclamp to both distract and compress the loop during placement or removalof the loop on an ossicle. The loop 3, the piston 4, and the rod 8 maybe formed from a biocompatible material such as titanium or an alloythereof. The spikes 2 may be formed from a material which simulates bonetissue, such as hydroxyapatite. Hydroxyapatite is desirable as it canfuse readily to natural bone tissue.

FIG. 2 is a perspective view of a stapes prosthesis 15 according to atleast one other aspect of the invention. The ossicle to which the stapesprosthesis 15 is engaged is omitted in FIG. 2 for clarity of the view.In the stapes prosthesis 15, a loop 13 which generally corresponds infunction and structure to the loop 3 of FIG. 1 is sufficiently broad soas to bear two rows of spikes 12. The spikes 12 may be similar infunction and structure to the spikes 2 of FIG. 1. Provision of two rowsof spikes 12 increases the area of the ossicle such as the incus 1 ofFIG. 1 which serves as a support surface for the stapes prosthesis 15,thereby increasing stability of contact over the single row of spikes 2seen in FIG. 1. Other than the spikes 12, the stapes prosthesis 15 maybe similar in structure and function to the stapes prosthesis 5 of FIG.1, such as by including a piston 14 and a rod 18, which may be thestructural and functional equivalents of the piston 4 and the rod 8 ofFIG. 1.

As depicted in FIG. 2, the rows of spikes 12 are staggered in that whenviewed from the end as illustrated in FIG. 1, all of the spikes 12 wouldbe seen because those spikes 12 farther from the observer may be locatedbetween adjacent spikes 12 of the row relatively closer to the observer.However, the spikes 12 may be disposed abreast of one another, oralternatively stated, not staggered if desired.

FIG. 3 shows further features of the invention. These features will bedescribed in terms of the stapes prosthesis 5 of FIG. 1, but will beunderstood to apply to any prosthesis according to the presentinvention. In one feature, a discrete projection 2A from the loop 3 maydiffer in length (called out by the reference numeral L1) and shape fromthe length (called out by the reference numeral L2) and shape of anotherspike 2B. The shape of the spike 2A may be somewhat bullet shaped,whereas the shape of the spike 2B may be substantially triangular. Ofcourse, other shapes and dimensions may be substituted for thoseexplicitly shown and described herein.

FIG. 4 shows still another feature of the invention, and again, will bedescribed in terms of the stapes prosthesis 5 of FIG. 1, but will beunderstood to apply to any prosthesis according to the presentinvention. A transition substance 10 may be disposed between the loop 3and the spikes, such as a spike 2C. This transition substance 10 may bea substance other than the constituent substance of the loop and theconstituent substance of the spikes. For example, the transitionsubstance 10 may be a polymeric material including a shape memorypolymeric material or a metal including shape memory metal. Shape memorymaterials are those which assume their original configuration afterforces which deform the object made from shape memory materials areremoved. Heat or other influences may be necessary to return a shapememory material object to its original configuration. Nitinol is anexample of a shape memory metal which may be employed. Should assemblyof the stapes prosthesis 5 deform the spikes 2, upon disassembly andwith heat or other necessary influences supplied, the spikes 2 willreassume their original configuration. For example, should assemblycause the spikes 2 to bend from an original perpendicular orientationrelative to the loop 3, if fabricated from shape memory materials theywill reassume the original perpendicular orientation when disassembledand heated if necessary to invoke the shape memory feature.

While the discrete projections such as the spikes 2 have been describedand shown as being tapered, there is no requirement that they be taperedin order to accomplish their mission of causing the loop of theprosthesis such as the loop 3 to be spaced apart from the bone such asthe incus 1. The projections may be cylindrical or flattened forexample, with or without points such as the points 7.

A prosthesis utilizing the attachment element shown in the stapesprosthesis 5 may be used to secure a foreign body such as a magnet to anossicle. The foreign body may perform a role of assisting in hearing, asis known in the art. The foreign body may comprise a magnet which issubjected to electrical or magnetic pulses so as to vibrate.

FIG. 5 shows an ossicular prosthesis 20 having an enlarged head 22 whichmay be attached by a rod 24 to a piston 26. The flattened configurationof the head 22 is typically used to interface with the malleus which isjust medial to, and in close contact with, the ear drum. The piston 26may sit in a fenestra (not shown) and communicate with the inner ear soas to pass vibrations in a manner approximating that which would occurshould all of the ossicles be undamaged. Alternatively, the rod mayconnect to another attachment element for fixation to another ossicle.The enlarged head 22 may generally assume the configuration of a dischaving a first principal face 28 bearing projections 30 which may be thestructural and functional equivalents of the projections or spikes 2 and12 of FIGS. 1 and 2, respectively. An opposed principal face 32 is thatfrom which the rod 24 projects. The rod serves as a vibrationtransmission element. The enlarged head 22 may have formed therein arecess 34 which is dimensioned and configured to seat an ossicle of themiddle ear and which comprises a surface 36 from which the projections30 project. The surface 36 may be curved and concave as shown.

Several variations of the enlarged head are possible. One variation isshown in FIG. 6, which shows an ossicular prosthesis 40 having anenlarged head 42 which may be attached by a rod 44 to a piston 46. Theenlarged head 42 may bear a recess 48 which may be centered on theenlarged head 42 in at least one view as seen, and which, apart from itslocation relative to the enlarged head 42 may be the structural andfunctional equivalent of the recess 34 of the prosthesis 20. The recess48 may bear projections 50 which may be the structural and functionalequivalents of the projections 30 of the ossicular prosthesis 20.

A further variation is shown in FIG. 7, which depicts an ossicularprosthesis 60 having an enlarged head 62 which may be attached by a rod64 to a piston 66 or an attachment element for another ossicle (notshown). Unlike the prostheses 20 and 40, the prosthesis 60 does not havea recess. Rather, projections 68 are fixed directly to a first principalface 70, with the rod 64 being fixed to an opposed second face 72. Theprojections 68 may be arrayed as a patch or linear array located offcenter on the enlarged head 62 as shown, or if desired, may be centeredon the enlarged head or may cover the entire enlarged head (theseoptions are not shown).

Notably, the embodiments shown in FIGS. 6 and 7 feature projections onlyin the area of the prosthesis which will contact an ossicle; other areasof the prosthesis which do not have projections will customarilyinterface with the soft tissue of the drum or other soft tissue placedadjacent to the drum by the surgeon. It is anticipated that ifprojections in this type of embodiment provide resistance to shearforces which tend to move the prosthesis away from the ossicle afterimplantation by the surgeon, then it will be more likely that theprosthesis will remain in the position it is placed by the surgeon andnot displace postoperatively.

It will be recognized that as employed herein, the term disc is intendedonly as a semantic convenience and should not be literally construed.The significance of a disc is that a disc presents two opposed principalor large faces among other surfaces, one which may support projectionssuch as the projections 2, 12, 30, 50, and 68 and optionally, a recesssuch as the recesses 34 and 48, and the other of which supports or iscoupled to the rod such as the rods 24, 44, and 64.

Regardless of the precise nature of a middle ear prosthesis according tothe present invention, it will be understood to comprise an ossicularattachment element which is dimensioned and configured to engage anossicle of the middle ear, such as the loop 3 or 13 or any of theenlarged heads 22, 42, and 62, a plurality of projections which projectfrom the ossicular attachment element in a direction facing the ossiclebeing engaged, such as the projections 2, 12, 30, 50, and 68, and avibration transmission element which is connected to the ossicularattachment element and dimensioned and configured to pass vibrationsconducted from the projections to another ossicle or directly to theinner ear, such as any of the rods 8, 18, 24, 44, and 64. Theprojections such as the projections 2, 12, 30, 50, and 68 collectivelydefine a discontinuous surface of dimensions and configuration tocontact and engage the ossicle of the middle ear in a manner capable ofsupporting the middle ear prosthesis in operable position to transmitvibrations and maintain firm contact with the ossicle, while reducingthe patch of contact between the prosthesis and the ossicle from thatwhich would be present in the absence of the projections such as theprojections 2, 12, 30, 50, and 68.

The vibration transmission element, which is in the above descriptionprovided by the rods 8, 18, 24, 44, and 64, may be devoid of a pistonsuch as the pistons 4, 14, 26, 46, and 66, should the end of the rods besufficient in dimensions and configuration to fulfill the functionprovided by the pistons. For example, rods may be tapered along theirlength and terminate in an end of dimensions greater than that at theenlarged head such as the loops 3 and 13, or the enlarged heads 22, 42,and 62.

It will be recognized by those of skill in the art that although thefigures illustrate a loop stapes prosthesis and a principal/opposedprincipal face design which is most often used to attach to the malleus,other prostheses which attach to any of the ossicles may utilize thenovel principles.

The invention may be thought of as the entire prosthesis, such as thestapes prostheses 5 and 15 or the prostheses 20, 40, and 60, oralternatively, as a substantial element of such a prosthesis. Forexample, the invention may be regarded as that portion of the stapesprosthesis 5 including the loop 3 and spikes 2, but may possibly notinclude the piston 4 or even the rod 8. If realized as a partialprosthesis, the invention may include a connector (not shown) enablingready attachment of the rod 8, piston 4, or other members furthering thefunction of the inventive prosthesis.

While particular embodiments of the invention have been described, it isnot intended that the invention be limited thereto. It is intended thatthe invention will be as broad in scope as the art will allow and thatthe application will be read likewise. Other embodiments for prosthesesutilizing the attachment design described can be utilized in situationsother than those involving attachment of a stapes prosthesis to theincus, or of the malleus to the stapes or stapes footplate. It cantherefore be appreciated by those skilled in the art that othersituations requiring secure attachment of a prosthesis to an ossicle canutilize the invention as claimed.

I claim:
 1. A middle ear prosthesis component, comprising: an ossicularattachment element that is dimensioned and configured to engage a firstossicle of a middle ear, the ossicular attachment element including adisc-shaped component having a first face and a second face; and aplurality of discrete projections that project from the first face ofthe disc-shaped component, each of the plurality of projections having(1) an elongated axis that projects from a surface of the first face ofthe disc-shaped component, and (2) a free end configured to contact andsecurely engage with the first ossicle in a manner that secures themiddle ear prosthesis component in an operable position with respect tothe first ossicle to transmit vibrations and to maintain contact withthe first ossicle, the plurality of discrete projections projecting fromonly a portion of the surface of the first face of the disc-shapedcomponent that describes a discrete area for ossicular contact, and thefirst face of the disc-shaped component being a substantially planarsurface area and the portion of the surface of the first face of thedisc-shaped component being a cavity in the substantially planar surfacearea, the elongated axis of each of the plurality of projectionsprojecting substantially orthogonally from a surface of the cavity. 2.The middle ear prosthesis component of claim 1, the free end of each ofthe plurality of discrete projections defining a point that isconfigured to at least partially penetrate a surface of the firstossicle to embed a portion of at least one of the plurality of discreteprojections in the first ossicle.
 3. The middle ear prosthesis componentof claim 1, the cavity in the substantially planar surface area beingdimensioned and configured to partially encircle the first ossicle. 4.The middle ear prosthesis component of claim 1, further comprising avibration transmission element attached to and projecting from thesecond face of the disc-shaped component, the vibration transmissionelement being dimensioned and configured to pass vibrations conductedfrom the plurality of discrete projections to an inner ear.
 5. Themiddle ear prosthesis component of claim 1, further comprising avibration transmission element attached to and projecting from thesecond face of the disc-shaped component, the vibration transmissionelement being dimensioned and configured to pass vibrations conductedfrom the first ossicle via the plurality of discrete projections to asecond ossicle via another ossicular attachment element contacting thesecond ossicle.
 6. The middle ear prosthesis component of claim 1, afirst group of the plurality of discrete projections having a firstshape and a second group of the plurality of discrete projections havinga second shape, the second shape being a different shape from the firstshape.
 7. The middle ear prosthesis of claim 1, the plurality ofdiscrete projections having varying lengths along respective elongatedaxes.
 8. The middle ear prosthesis component of claim 1, furthercomprising an additional body component configured to be secured to thefirst ossicle.
 9. The middle ear prosthesis component of claim 8, theadditional body component being a magnet.